Objective:

This grant funded interdisciplinary research to address the following broad questions: How will emerging technologies and infrastructure changes (including transportation) and global climate and air pollution policies impact regional air quality by 2050? How will urban and regional landscapes evolve in response to changes in production and distribution at regional and global scales? How will associated changes in land use affect emissions and air quality? How will regional and national policy decisions affect the urban landscape and what are the implications for air quality under future climate scenarios? What are the synergies between climate and air quality regulation? How can the results of these studies best be used to inform present and future policy decisions?

Summary/Accomplishments (Outputs/Outcomes):

The stylized facts of freight movement in the United States are such that the movement of intermediate and final-demand goods is increasing at an annual rate of growth that is three times the annual rate of growth of gross domestic product (GDP). While the rise in intra-industry trade (IIT) accounts for much of the increase in the transport intensity of production, the time series we have produced for this study shows that IIT is variable between industries. We hypothesize that it is likely that an increase in through traffic (of freight, say, from Southeast Asian producers) accounts for much, though certainly not all, of the growth in freight movement. We also have found that increases in freight movement and technical changes in transport fuel use, resulting in decreasing non-point-source emissions associated with freight movement, have been somewhat offsetting, resulting in somewhat stable patterns in emissions associated with freight movement in recent years. This pattern could change as limits of technological improvement are reached and congestion of major transport arteries increases.

Corresponding to changes in freight movement between locations have been changes in economic geography, or spatial patterns of production and use and consumption of goods and services. Industrial activities have been reconfigured—in many cases fragmented—to exploit decreasing transport costs, lowered trade barriers, the global reach of information technologies, and economies of scale and scope that can be realized by clustering complementary activities in locations that favor them. This reconfiguration has resulted in the ‘hollowing out’ of regional economies as local purchases have been reduced in favor of purchasing intermediate goods through far-flung supply chains. The structural-equation modeling we have conducted suggests that there is strong empirical support for the so-called ‘new economic geography’ (NEG) of Nobel laureate Paul Krugman, Masahisa Fujita, and Anthony Venables—in fact this is one of the first studies to actually confront NEG hypotheses with data—according to which firms competing in imperfectly competitive markets exploit economies of scale and scope, are sourced from multiple locations, and substitute comparable inputs from different locations on the basis of delivered prices.

In this study, we have worked with published data, received theory, and proven methods to 1) derive time-series data on freight movement that heretofore did not exist in order to 2) calibrate models that also previously did not exist to 3) examine questions about the likely impacts of continued trends in globalization and infrastructure systems that may or may not be able to accommodate these trends on emissions and air quality and to 4) examine the change geographic structure of black carbon emissions from 1997-2007 within the Midwestern and Northeastern United States. In particular, we have generated spatial time-series on interstate inter-industry freight flows, calculated associated non-point source emissions, estimated the parameters of a structural-equation model characterizing the evolution of freight flows and activities on the ground giving rise to them, and operationalized a commodity–flow model with associated emissions.

We have calculated the black carbon emissions from commodity flows in the Midwestern and Northeastern United States from 1977-2007. The resulting emissions of black carbon have been compared against existing emission inventories. We have characterized how the potential emission growth from the continued increase in freight tonnage in the Midwestern and Northeastern United States is counteracted by decreases in the BC emission factor of heavy-duty diesel trucks, which results in an overall decrease of BC emissions by 2007. The increase in transportation volumes is consistent with a transformation of the transportation sector as a part of an increasingly interconnected global economy that is dependent on just-in-time deliveries of both intermediate and finished commodities. Relative to the population proxy methodology of many inventories our methodology has redistributed a portion of the BC emissions away from urban areas and towards the transportation corridors. We ascribe the differences in sub-regional trends in BC emissions to regional changes in the producers of finished and semi-finished goods and the freight distribution system, which connects them, all under the influence of broader scale globalization. The framework established in this study can be used to estimate future BC transportation emissions under a set of stylized economic, technological, and regulatory scenarios.

We also have examined the ability of climate models to simulate regional air quality when run using simulated meteorology (General Circulation Models or GCMs). Although we recommend caution in the use of GCMs to simulate air quality, we found that while a simulation using analyzed meteorology best simulates temperatures, it did not outperform GCMs in other metrics. We find simulations using 56 vertical levels generally outperform 26 level versions in capturing ozone-temperature relationships and ozone extreme values, although the 26-level simulation is generally used in climate simulations.

We also have updated the present-day emission scenario so as to conduct air quality simulations using a recently developed aerosol tagging mechanism in the Community Earth System Model (CESM). The updates include a more realistic transportation network, which links each region’s transportation node through the shortest-distance interstate highway. This new transportation network improves upon the previous stylized transportation network and results in more concentration of BC emissions around the interstate highways. This formulation differs from existing BC emissions inventories that largely distribute emissions via a population proxy, thus neglecting populations in rural areas near transportation corridors. A number of future scenarios have been developed. We are completing research into implementing future black carbon emissions into a chemistry-climate model so as to examine the impact of the resulting emissions on PM2.5. To date, we have not fully succeeded in operationalizing a fully dynamic network model or linking the network model to local transportation-land-use planning models.

Brown-Steiner B, Hess PG. Asian influence on surface ozone in the United States: a comparison of chemistry, seasonality, and transport mechanisms. Journal of Geophysical Research 2011;116(D17):D17309 (13 pp.).

Brown-Steiner B, Hess PG, Lin MY. On the capabilities and limitations of GCCM simulations of summertime regional air quality:a diagnostic analysis of ozone and temperature simulations in the US using CESM CAM-Chem. Atmospheric Environment 2015;101:134-148.

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.